What is Aluminum Anodizing?

Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish(Al2O3). For CNC machining, Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.While anodizing does work for several other base materials, aluminum responds the most effectively to anodizing.

Why to Make Anodizing?

First for preventing corrosion and abrasion. Pure aluminum does not easily corrode because of this. However, aluminum that contains other alloying elements can be subject to corrosion unless a thick aluminum oxide layer can be made to protect it.

The anodic oxide structure originates from the aluminum substrate and is composed entirely of aluminum oxide. This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel.

Second for decoration.The aluminum oxide layer that is created on an aluminum alloy during the anodizing process is porous. This allows some dyes to be absorbed by the oxide layer. Aluminum alloys that couldn’t be dyed before can now be made to be a variety of colors.

What is Hard Anodizing?

Hard anodized coatings (standard[MIL-A-8625F] Type III, Class 1 & 2) are typically applied to heavy wear industrial parts intended for use in aggressive or highly corrosive applications. These coatings are typically far thicker and harder than decorative ones, and usually lend the parts a durability approaching that of hard faced or case hardened steel.

Hard anodized parts have coatings which exceed 10 μm with typical coatings exceeding 25 μm.

Hardcoated items usually have a dark gray, matte finish, although this can vary depending on the metal the item is made of and the composition of the electrolyte solution.

What is Decorative Anodizing?

Decorative anodizing usually features coatings of less than 10 μm and, although durable, doesn't have the same exceptional wear characteristics of hard anodizing.

The good thing for decorative anodizing is you can choose whatever color you want.